This project, directed toward elucidating the molecular mechanisms responsible for cataractogenesis, places special emphasis on the role of the structure and function of the lens crystallins. One system under study involves a guinea pig hereditary congenital cataract that results from a mutation in the gene for a major lens protein, zeta- crystallin. This protein is an enzyme/crystallin, a protein with two distinct functions. We are investigating how the mutation affects both zeta-crystallin's catalytic function as a quinone reductase and its structural role as a lens crystallin. Because this protein is a crystallin in only a few species and is present at just catalytic levels in most species, it is an excellent system to use in analyzing lens- specific protein expression. Studies on the promoters for the zeta gene in several species indicate the presence of a second lens- specific promoter only in a species (i.e., guinea pig) that has high expression of zeta-crystallin in the lens. A second focus of this project concerns the putative role of alpha- crystallin as a molecular chaperon. Studies by our group have confirmed that alpha-crystallin binds denaturing proteins, thus preventing their aggregation. Our current studies involve the nature and stability of the complex produced and the role such complex formation may play in the remarkable ability of the lens to remain transparent for decades, even though it has very limited synthesis and repair capabilities. A major new initiative of our group concerns utilization of lens organ culture as a means of identifying therapeutic agents with efficacy as anticataract agents. Our studies have involved several cataract- inducing systems and a number of potential anticataract agents, including those with antioxidant activity.